High-Pressure Fuel Pump: Everything You Should Know

A high-pressure fuel pump must regulate the amount of fuel that is compressed because it is unable to increase its speed without the engine’s increased output or pressure. This connection is what some technicians and even engineers find confusing about direct injection high-pressure fuel pumps. However, your diagnostic abilities will advance once you comprehend the connection between the control solenoid and the pump.

Table of Contents

What is a High-Pressure Fuel Pump?

Gasoline direct injection engines are more “evolved” than regular engines. They are made to directly inject fuel under high pressure into each cylinder’s combustion chamber. This brings several benefits:

Better emissions
Improved fuel economy
More power

The GDI engine technology has been around since the 1990s. Its popularity of it, however, is still in its early stages. It’s because automakers consider it to be a good way to meet the increasingly stringent emissions and fuel economy standards set by state governments.

Higher fuel pressure is required by GDI engines. High-pressure GDI fuel pumps can help with that.

What Does a High-Pressure Fuel Pump Do?

The high-pressure fuel pump is the piece of machinery responsible for injecting fuel into the combustion chamber of your engine, which allows your car to run more efficiently. The design of the engine makes it so that if the fuel pump fails, there won’t be any fuel in the engine.

How Does a High-Pressure Fuel Pump Work?

The most modern mechanical fuel pumps are high-pressure GDI pumps. A high enough pressure must be produced by a high-pressure fuel pump in order for the fuel to completely atomize. This is necessary for the engine to function properly. A GDI system has two fuel pumps:

An in-tank pump that’s responsible for pumping enough fuel to the engine
A high-pressure GDI fuel pump that’s responsible for creating enough pressure

The engine must mechanically drive high-pressure GDI fuel pumps due to their high power requirements. Usually, the camshaft is used to power a high-pressure GDI fuel pump. When the engine starts, the pump also starts. Because of this configuration, the fuel pump and engine remain in close proximity. By doing this, the engine is guaranteed to receive the proper fuel pressure at all times.

A mechanical fuel pump is similar to a high-pressure GDI fuel pump in design, but the latter is more modern. Its function is to pressurize fuel entering the fuel tank before it is sent to the fuel rail.

The GDI system includes a fuel pressure sensor. The sensor assists the powertrain control module (PCM) in adjusting the volume of fuel entering the pump inlet. A high-pressure GDI pump typically generates around 2,000 psi. In order to maintain the fuel pressure at the ideal level for the engine in real-time, the sensor and PCM assist in pressure regulation.

When the in-tank pump sends fuel to the high-pressure GDI fuel pump, this is what happens:

Through the top of the high-pressure GDI fuel pump, low-pressure fuel enters the system.
The fuel is forced into the pumping chamber by the armature rod, which is connected to the control valve plate.
The plunger is pushed into the pumping chamber by the camshaft. This cramps the area and pushes the fuel into the rail. This causes the fuel to “shoot out” of the pump.

The plunger is quickly raised and lowered by the camshaft. Consistently, this process happens. The PCM regulates how much fuel enters the high-pressure GDI fuel pump with the aid of the fuel pressure sensor.

What is the DESIGN and FUNCTION of a High-Pressure Fuel Pump?

Different high-pressure pumps can be installed depending on the vehicle’s manufacturer and engine design. Here, the three types of pumps—radial piston pumps, axial piston pumps, and in-line pumps—that can be operated with one or more pump elements are distinguished. Due to the various drive concepts, either fuel or engine oil can be used to lubricate the pump.

No matter the design, the job of the high-pressure fuel pump is to compress the fuel delivered by the pre-feed pump to the fuel pressure needed for the injection valves and then to make it accessible in the fuel distribution pipe (rail). The delivery rate of the high-pressure pump is inversely proportional to engine speed because it is mechanically driven by the camshafts.

The engine control unit keeps track of the fuel pressure using a pressure sensor, and the pump’s flow control valve regulates it. Directly attached to the high-pressure pump is this fuel pressure regulator. It gauges the high-pressure pump’s supply and controls its operation in this way.

Only the high pressure that is actually required for the current operating situation is generated in the pump thanks to this demand-based control.

What Are the Symptoms of a Failing High-Pressure Fuel Pump?

Symptoms of a high-pressure fuel pump failure are:

The engine starts with a delay.
acceleration that sputters or hesitates between 2000 and 4000 RPM.
elevated engine temperatures.
vehicle stalls because of heat or effort.
Measurements on the fuel pressure gauge are low.
Poor gas mileage.

What Causes of High-Pressure Fuel Pump FAILURE?

The high-pressure pump may eventually become defective due to severe mechanical strain, high fuel pressures, a lack of lubricant, and temperature variations that promote wear.

The Following Effects May Indicate a Defective High-pressure Pump

Erratic engine running
No power in the upper-speed range
Poor starting behavior
Engine stops – engine warning light comes on
Oil dilution

The causes of Failure of the High-pressure Pump Can Be as Follows

External mechanical damage
Internal mechanical damage to the drive, roller tappet or pump element
Leaks – fuel loss
Inspection service intervals/maintenance intervals not observed
Poor lubrication – oil dilution or poor oil quality
Contamination in the low-pressure system

How to Test and Fault Diagnoses for High-Pressure Fuel Pump?

The relevant higher-level engine control unit keeps track of the high-pressure fuel pump’s operation. Pressure sensors are used to identify and store errors that affect the system pressure in the control unit. The system parameters and error codes can be read out and used for additional troubleshooting with the help of a suitable diagnostic device. The engine warning lamp in the instrument cluster will illuminate to alert the driver to a system-relevant fault.

The diagnostic data that follows is presented using examples from various vehicles.

Visual Inspection

The individual system components should first be visually inspected as part of the initial troubleshooting steps before control unit diagnostics are started. This allows for the early detection and remediation of fuel line leaks as well as damaged sensor plug connections.

Reading the Error Memory

This function allows for the reading and deletion of error codes that have been saved in the error memory. Additionally, the error code’s information can be called up.

In our case study, the fuel pressure control valve’s electrical plug connection was broken, which caused the error code P2294 to be recorded in the error memory.

Error code P2294 – fuel pressure regulator/solenoid valve

Break in the circuit
Signal missing / no communication
Error permanent reading off parameters

The high and low-pressure sensor parameters from the control unit should be examined first in order to check and evaluate the system pressures.

Additionally, it is possible to compare the displayed actual values with the target values established by the vehicle manufacturer in order to identify potential sources of errors.

After the low-pressure circuit has been tested and no errors have been found, the high-pressure circuit is always tested.

Checking Fuel Low Pressure

The feed line to the high-pressure pump is where the low-fuel pressure sensor is installed, and it communicates with the engine control unit by sending a signal.

With the aid of this data, the engine control unit can determine the necessary low pressure and send the signal to the fuel pump control unit for demand-based pump activation.

In a typical setting, the pre-supply pressure is approximate. 4.0 bar
Pre-supply pressure of approximately for cold or hot starts at 7.0 bar

When a sensor is faulty, the engine control unit controls the pre-supply pump with a fixed value and raises the pressure as a result. The pre-supply pump won’t operate if the fuel pump control unit is broken.

Checking Fuel High Pressure

In order to communicate with the engine control unit, the fuel pressure sensor for high pressure is screwed into the distributor pipe (rail). The engine control unit analyzes the data, and then the high pressure is adjusted appropriately using the high-pressure control valve. The control unit activates the control valve with a fixed substitute value in the event of a damaged sensor.

How Long Should a High-Pressure Fuel Pump Last?

Your car’s unheralded hero is the fuel pump. For your car, truck, or SUV to start and run, it draws fuel from the gas tank and sends it to the engine. Your vehicle’s fuel pump should last at least 100,000 miles or more.

How Much Does a High-Pressure Fuel Pump Cost?

The average cost for a fuel pump replacement is between $220 and $1,062, depending on the vehicle and age. While parts range in price from $95 to $854, labor costs are predicted to be between $124 and $260.

How Much Does It Cost to Replace a High-Pressure Fuel Pump?

Can I Drive With a Faulty High-Pressure Fuel Pump?

Because a bad fuel pump could cause unexpected drops in power or even completely shut the vehicle down, we do not recommend driving with the knowledge of a bad fuel pump.

Do you know more about high-pressure fuel pumps?